1. Field of the Invention
This application is directed toward adjustment mechanisms, which can be incorporated in furniture, such as office furniture, and more particularly to a chair back height adjustment mechanism.
2. Description of the Related Art
Many specialized types of seating furniture benefit from adjustability of their parts to conform to the particular size of the individual sitting on the furniture. This may include back height adjustment, seat tilt or forward/back extension adjustment, lumbar adjustment, etc. Chairs of this kind may also include armrests that adjust in height relative to the chair body.
In some configurations, components of adjustable office chairs are adjusted with a rotatable knob which controls a frictional clamping relationship. One hand may be used to adjust the height of adjustable member and the other hand may be used to rotate the knob to clamp the adjustable member at a desired height. However, this mechanism requires the user to first rotate the knob to release the clamping force and then rotate the knob again to re-engage the clamping force. This requires a significant amount of hand strength and, thus, may be difficult for some users to perform.
Other chair adjustment mechanisms include a lever-based system in which teeth of the adjustment mechanism engage slots or notches. Typically, such mechanisms allow adjustment only in discrete, predetermined intervals. Furthermore, adjustment of a chair back in a reverse direction (such as down) may only be done after pulling the chair back fully in one direction (such as up), to release the mechanism and allow the adjustment mechanism to reset.
These types of adjusting mechanisms are common due to being uncomplicated and inexpensive to produce. However, these designs have substantial disadvantages in that they are not infinitely adjustable and/or are not easy to adjust with one hand. Additionally, a set-screw-type connection may require substantial force to insure that the part to be adjusted does not slip from its desired position. This may cause user discomfort and may be difficult for some users to operate.